This invention relates to scanners and, more particularly, to a mechanical step scanner adapted for use in providing high-resolution, high-speed image tracking.
To provide such high-resolution, high-speed image tracking, it may be necessary to dissect the image into segments, sections, blocks or the like for data acquisition. If such action is necessary, then the image may be dissected into (and the data for each segment, or the like, may be acquired in) a serial (i.e., sequential) fashion by a multi-element detector array. Therefore, it is desirable to move the image relative to the array in a precise and systematic manner. In an active tracker synchronized step scanning devices may be employed in both the transmitter and the receiver optical paths to illuminate the target and to receive the reflected energy. For a passive tracking system, these same stepped scan devices may be employed to move the image relative to the detector array. My inventive stepped scanner, described herein, is a mechanical means of providing step scanning of either a transmitter or of a receiver optical path.
Generally, scanning devices are mechanized with a linear or harmonic motion which moves an optical surface to change the angle of reflection of the optical path to image it on to the detector surfaces. My inventive scanner, however, moves the image relative to the detector array in a systematic manner in a step-wise fashion by displacing, rather than by deflecting, the optical path. In this manner, the stepping motion is independent of the physical dimensions between the scanner device and the array. In fact, the scanner device can be placed immediately ahead of the array, in a region where the cross section of the focused optical beam is relatively small; whereas, in a typical deflection-type scanner of the prior art, the deflection angle is inversely proportional to the distance between the scanner and the detector array, and thus to keep the deflection angle small, the array must be displaced from the scanner by relatively large distances.
Further, in a deflection scanner the reflective surfaces must be helical or conical surfaces. These surfaces will yield aberration of the image in the direction parallel to the motion of the reflective surface. In my displacement scanner, the reflective surfaces are all optically flat and parallel. The planes of these surfaces are normal to their axis of rotation. This greatly simplifies the manufacture and alignment of my inventive scanner device, and eliminates any aberration of the image.